1. The field of art to which the invention pertains includes the art of fluid handling as specifically directed toward tapping a pipe main under pressure.
2. Tapping sleeve service connectors for effecting a house outlet connection are available from a variety of manufacturers and are widely used for tapping gas service from underground gas mains. Typically, such tapping service connectors include a body having a side outlet house connection integral therewith and adapted for mounting in a surrounding relation onto the exterior of the pipe main. The tapping tool is threadedly supported in the body for radial advancement against the pipe wall until effecting a penetration or cutting of a removable slug by which an opening is formed that will communicate with the branch connection. Once the opening is formed it is of course essential that alignment with the tapping tool be maintained both to ensure continued gas flow through the branch opening and to provide for the eventual possibility that the tapping tool may be needed to shut off the opening.
By and large the majority of prior art applications for such tapping sleeves has included a cast or forged service connector suitable for mounting on a gas main of schedule 40 steel pipe usually of six inch diameter or larger. Conventional mounting of the sleeve onto the main usually produced a grip of magnitude sufficient to resist any slippage rotation therebetween as might be imposed by the turning moment of the branch connection. In recent years with the advent of plastic for gas service components, one or the other of the service connector or pipe has been of plastic composition. This has presented at least one relatively soft gripping surface along with a reduced coefficient of friction therebetween afforded by the substantially smooth surface finish of the plastic component. For overcoming the potential slippage of this combination it has been common to employ an intervening abrasive material such as emery cloth to secure the necessary rotational interlock. To ensure effectiveness of the emery cloth in that relationship it was necessary to prebond its smooth backside to the gripping faces of the connector sleeve.
While such prior art techniques have been generally satisfactory for achieving the gripping relation necessary to prevent rotation between metal sleeve and plastic pipe, it is generally inadequate where both the service connector and gas main are of plastic composition. That is, in the plastic-to-plastic situation both gripping surfaces are relatively flexible and smooth and lack sufficient structural rigidity to withstand a clamping force necessary to overcome the relative absence of a friction coefficient. The problem becomes increasingly acute with increase in nominal pipe size as the lateral distance between the pipe and outlet is increased thereby increasing the moment arm thereat. It is further complicated by a general inability to obtain an adequate bond of the smooth side of emery cloth to either of the gripping surfaces. Despite recognition of these problems, a ready and practical solution has not heretofore been known.